Fundamentals of Deep-Subwavelength Near-Field Imaging With Hyperbolic Polaritons

Interface polaritons with extreme electromagnetic confinement enable near-field imaging with resolution far beyond the diffraction limit. Natural polaritonic materials supporting low-loss and anisotropic polariton modes have emerged as versatile platforms for deep-subwavelength imaging, yet the fundamental limits of their resolving power remain unexplored. Here, we uncover the intrinsic resolution limit of polaritonic imaging by linking it to the linewidth of hyperbolic polariton beams, which originates from the material's optical properties and scales linearly with thickness. By exploiting negative refraction in vertically stacked heterostructures, we further propose a strategy to achieve scalar fidelity under proper thickness configurations and reveal a potential pathway to mitigating geometrical distortion in polaritonic imaging. Our findings elucidate the fundamental physics of near-field imaging with hyperbolic polaritons, providing guiding principles for improving both its scalar and geometrical fidelity toward practical applications.